1. Field of the Invention
The present invention relates to an in-cylinder fuel injection valve for directly injecting fuel into the combustion chamber of an internal combustion engine from an injection port by turning the fuel.
2. Description of the Prior Art
FIG. 8 is an axial direction sectional view showing a fuel injection valve disclosed by Japanese Laid-open Patent Application No. 2-215963, and FIG. 9 is a perspective view showing a turning body in the fuel injection valve of FIG. 8. In FIG. 8, reference numeral 51 denotes a valve housing, 52 a solenoid unit installed in the valve housing 51, 53 the core of the solenoid unit 52, 54 the electromagnetic coil of the solenoid unit 52, 55 the plunger of the solenoid unit 52, 56 the spring force control bar of the solenoid unit 52, 57 the spring of the solenoid unit 52, 58 the terminal of the solenoid unit 52, 59 a valve unit attached to an end portion of the valve housing 51 in such a manner that it becomes coaxial to the solenoid unit 52, 60 the valve body of the valve unit 59, 61 the ball valve of the valve unit 59, 62 a valve seat formed in the valve body 60, 63 an injection port formed in the valve body 60, 64 the turning body of the valve unit 59, 65 a center hole formed in the turning body 64 to support the ball valve 61 so that it can move in an axial direction, 66 a vertical passage formed around the turning body 64, 67 turning grooves formed in the valve body side of the turning body 64, 68 a fuel supply hole formed in the valve housing 51, 69 a fuel passage formed in a space between the valve housing 51 and the solenoid unit 52, and 70 a fuel pipe fitted onto the valve housing 51. In FIG. 9, the turning grooves 67 are connected to the injection port 63 eccentric to the center of the turning body 64.
A description is subsequently given of the operation of the above prior art. Fuel is guided into the turning grooves 67 from the fuel pipe 70 through the fuel supply hole 68, the fuel passage 69 and the vertical passage 66. When electricity to be supplied from the terminal 58 to the electromagnetic coil 54 is cut, the plunger 55 is pressed by the spring force of the spring 57, and the ball valve 61 contacts the valve seat 62 to stop a flow of fuel from the turning grooves 67 to the injection port 63. When electricity is applied to the electromagnetic coil 54 from the terminal 58 while the valve unit 59 is thus closed by the spring force of the spring 57, a magnetic circuit is formed by the electromagnetic coil 54, the core 53, the valve housing 51 and the plunger 55, the plunger 55 and the ball valve 61 are magnetically attracted toward the core 53 side, and an annular space is formed between the ball valve 61 and the valve seat 62. That is, when the valve unit 59 is opened by the electromagnetic attraction of the solenoid unit 52, the annular space is formed between the ball valve 61 and the valve seat 62 and fuel is injected into the injection port 63 through the annular space from the turning grooves 67. Since the turning grooves 67 are eccentric to the center of the turning body 64, fuel turns along the lower peripheral surface of the ball valve 61 from the turning grooves 67, passes through the annular space and is injected from the injection port 63 in a conical spray form having a predetermined angle.
FIG. 12 is an axial direction sectional view showing a in-cylinder fuel injection valve disclosed by Japanese Laid-open Patent Application No. 10-47208. In FIG. 12, reference numeral 1 denotes a first valve housing constituting a front half of a valve housing, 2 a second valve housing constituting a rear half of the valve housing and fixed coaxial to the rear end of the first valve housing 1, 3 a valve unit installed in the first valve housing 1, 4 a spacer set in the first valve housing 1, 5 an internal passage formed in the spacer 4, 6 a valve body installed in the first valve housing 1, 7 an internal passage formed in the valve body 6, 8 a storage chamber formed in the end portion of the valve body 6 such that it is coaxial to the internal passage 7 and having a diameter larger than that of the internal passage 7, 9 a needle valve as a valve stored in the spacer 4 and the valve body 6 through the internal passage 7 in such a manner that it can move in an axial direction, 10 a holder connected to the outer side portion of the end of the first valve housing 1 to fix the spacer 4 and the valve body 6 to the first valve housing 1, 11 the turning body of the valve unit 3 stored in the storage chamber 8, 12 a center hole formed in the turning body 11 to support the needle valve 9 such that it can move in an axial direction, 13 a horizontal passage formed along the top surface of the turning body 11, 14 a vertical passage formed around the turning body 11, 15 an inner annular groove formed annular in the under surface of the turning body 11 outside the center hole 12, and 16 turning grooves formed in the under surface of the turning body 11 such that they communicate with the vertical passage 14 and the inner annular groove 15. The turning grooves 16 are connected to the inner annular groove 15 tangentially.
Denoted by 17 is a valve seat stored and fixed airtightly in the storage chamber 8 of the valve body 6 in such a manner that it is placed under the turning body 11, 18 a valve seat surface formed on the top of the valve seat 17, 19 an injection port formed in the center of the valve seat 18 coaxial to the valve seat 17, and 20 a sealing member for the valve unit 3 fitted in a contact portion between the first valve housing 1 and the valve body 6 to prevent the leakage of fuel. Reference numeral 21 represents a solenoid unit installed in the first valve housing 1 and the second valve housing 2 such that it is coaxial to the valve unit 3, 22 a core installed in the first valve housing 1 and the second valve housing 2, 23 an internal passage formed in the core 22, 24 a sleeve fitted in the core 22 at an intermediate portion of the internal passage 23, 25 an internal passage formed in the sleeve 24, 26 a bobbin installed in the first valve housing and fitted onto the end portion of the core 22, 27 an electromagnetic coil fitted onto the bobbin 26, 28 a sealing member fitted in contact portions among the first valve housing 1, the core 22 and the bobbin 26 to prevent the leakage of fuel, and 29 an armature stored in the first valve housing 1 below the core 22 such that it can move an axial direction. The armature 29 supports the top portion of the needle valve 9. Denoted by 30 is an internal passage formed around the armature 29, 31 a spring inserted between the sleeve 24 and the armature 29 in the internal passage 23, 32 a terminal connected to the electromagnetic coil 27, 33 a filter installed in the internal passage 23 which is a fuel inlet portion, 34 a fuel pipe connected to the second valve housing 2 and the core 22 around the filter 33, and 35 the cylinder block of an internal combustion engine equipped with an in-cylinder fuel injection valve.
The valve unit 3 comprises the spacer 4, internal passage 5, valve body 6, internal passage 7, storage chamber 8, needle valve 9, turning body 11, center hole 12, horizontal passage 13, vertical passage 14, inner annular groove 15, turning grooves 16, valve seat 17, valve seat surface 18 and injection port 19. The solenoid unit 21 comprises the core 22, internal passage 23, sleeve 24, internal passage 25, bobbin 26, electromagnetic coil 27, armature 29, internal passage 30, spring 31 and terminal 32.
A description is subsequently given of the operation of the in-cylinder fuel injection valve shown in FIG. 12. Fuel is guided into the inner annular groove 15 from the fuel pipe 34 through the filter 33, internal passages 25, 23, 30, 5 and 7, horizontal passage 13, vertical passage 14 and turning grooves 16. When electricity to be applied from the terminal 32 to the electromagnetic coil 27 is cut, the armature 29 is pressed by the spring force of the spring 31, and the needle valve 9 is contacted to the valve seat surface 18 by the armature 29 to stop a flow of fuel from the inner annular groove 15 to the injection port 19. When electricity is applied to the electromagnetic coil 27 from the terminal 32 while the valve unit 3 is thus closed by the spring force of the spring 31, a magnetic circuit is formed by the electromagnetic coil 27, the core 22, the first valve housing 1 and the armature 29, the armature is magnetically attracted toward the core 22 side, the needle valve 9 moves up in an axial direction together with the armature 29, and an annular space is formed between the needle valve 9 and the valve seat surface 18. That is, when the valve unit 13 is opened by the electromagnetic attraction of the solenoid unit 21, the annular space is formed between the needle valve 9 and the valve seat surface 18 and fuel is injected into the injection port 19 from the inner annular groove 15 through the above annular space. Since the turning grooves 16 are connected to the inner annular groove 15 tangentially, fuel flowing into the inner annular groove 15 from the turning grooves 16 turns along the inner annular groove 15, passes through the above annular space and is injected from the injection port 19 in a conical spray form having a predetermined angle.
As for the fuel injection valve of FIG. 8, when the spray form of fuel injected from the injection port 63 through the turning grooves 67 and the annular space between the ball valve 61 and the valve seat surface 62 by the opening of the valve unit 59 caused by the electromagnetic attraction of the solenoid unit 52 was measured, the results shown in FIG. 10 and FIG. 11 were obtained. FIG. 10 and FIG. 11 are horizontal direction sectional views showing the spray forms of fuel injected from the injection port 63. In FIG. 10, the spray form 71 of fuel is polygonal influenced by the number of the turning grooves 67 as shown by slant lines and in FIG. 11, the spray form 72 of fuel is nonuniform in a circumferential direction and eccentric as shown by slant lines. From FIG. 10 and FIG. 11, the reason for the above spray forms is considered to be that fuel is not turned fully in the step where it flows into the annular space between the ball valve 61 and the valve seat surface 62 from the turning grooves 67 because the fuel injection valve of FIG. 8 has such a structure that the turning grooves are directly connected to the injection port 63 as described above.
As for the in-cylinder fuel injection valve of FIG. 12, when the spray form of fuel injected from the injection port 19 through the turning grooves 16, the inner annular groove 15 and the annular space between the needle valve 9 and the valve seat surface 18 by the opening of the valve unit 3 caused by the electromagnetic attraction of the solenoid unit 21 was measured, the results shown in FIG. 13 and FIG. 14 were obtained. FIG. 13 is an axial direction sectional view showing the spray form of fuel injected from the injection port 19 and FIG. 14 is a horizontal direction sectional view showing the spray form of fuel injected from the injection port 19. In FIG. 13 and FIG. 14, the spray form 38 of fuel is a perfect hollow cone having center spray 37 with the injection port 19 as a center. From FIG. 13 and FIG. 14, the reason for this spray form is considered to be that when the width of the inner annular groove 15 is larger than a predetermined value, fuel which is not turned when the valve unit 3 is opened is injected ahead, thereby generating center spray 37 in which fuel is not atomized, although fuel receives turning energy fully from the inner annular groove 15 and a uniform spray form 39 in a circumferential direction can be thereby obtained as shown by slant lines in FIG. 14 because the in-cylinder fuel injection valve of FIG. 12 has such a structure that the turning grooves 16 communicate with the injection port 19 through the inner annular groove 15 and are connected to the inner annular groove 15 tangentially.
As for the in-cylinder fuel injection valve of FIG. 12, when the spray distribution of fuel injected from the injection port 19 was measured, the results shown in FIG. 15 were obtained. This measurement was carried out by placing a plurality of concentric jigs having different diameters at each spray solid angle .theta. (see FIG. 13) from the center of spray coaxial to the injection port 19, 50 mm away from the injection port 19 and right below the injection port 19. The amount of spray received by these jigs which receive the spray of fuel injected from the injection port 19 was measured. FIG. 15 is a diagram showing the results of this measurement, plotting the proportion of the amount of spray received by each jig at each spray solid angle .theta. to the total amount of spray received by all the jigs. It is understood from FIG. 15 that the proportion of the amount of spray gradually decreases to 16 to 5.5% when the spray solid angle is 5 to 18.degree., sharply increases to 5.5 to 32% when the spray solid angle is 18 to 35.degree., becomes maximum at 32% when the spray solid angle is 35.degree., and sharply decreases to 32 to 10% when the spray solid angle is 35 to 45.degree..
As an example of combustion of fuel injected into the cylinders of an internal combustion engine, the spray of fuel is reflected by the top face of a piston and concentrated around an ignition plug to form a concentrated mixed gas and center spray which leads the implementation of the combustion of a formed layer may be necessary. However, in an internal combustion engine in which the best combustion is achieved by implementing perfectly hollow conical spray without using a system in which the spray of fuel is not reflected by the top face of the piston, it is ideal that the amount of center spray should be minimum.